If no any curing measure is taken for concrete against natural setting or hardening, substantial water losses will occur due to fast water evaporation, thus prevents cement from hydration and leads to dusting or drying crack on concrete surface. In such case, the strength and durability of concrete will be reduced. After placing of concrete, curing shall be duly required to avoid water loss and drying crack. External curing is generally required for concrete after placing. In other words, water spraying or covering by plastic membrane or burlaps is applied to concrete surface to maintain enough moisture, namely, so-called “moist curing” is performed to ensure full cement hydration for a higher compressive strength. However, “moist curing” method needs regular maintenance such as manual watering, sprinkling or spraying, while repetitive wetting and drying will result in cracks against structural integrity.
In addition, available common methods for curing concrete include membrane curing and water-proof covering. According to membrane curing method, when liquid membrane-forming compounds for curing concrete (also referred to as membrane protective agent) is sprayed onto fresh concrete surface, the curing agent will rapidly form a water-proof film on the concrete surface, which prevents water evaporation and provides hydration conditions for cement. The curing agents, which are generally made of silica gel or latex film, can easily aggregate at depressed concrete surface, thus reducing the surface friction coefficient. Water-proof covering method applies only to large-sized simple structure. Despite of domestic and foreign regulations on “proper curing”, the relevant research shows that, even the most fundamental curing requirements are not met, or totally ignored in practical engineering.